[PATCH v7 1/3] bus: mhi: host: add mhi_power_down_keep_dev()

Baochen Qiang
2024-03-05T02:13:51Z

ath11k fails to resume:

ath11k_pci 0000:06:00.0: timeout while waiting for restart complete

This happens because when calling mhi_sync_power_up() the MHI subsystem
eventually calls device_add() from mhi_create_devices() but the device
creation is deferred:

mhi mhi0_IPCR: Driver qcom_mhi_qrtr force probe deferral

The reason for deferring device creation is explained in dpm_prepare():

/*
* It is unsafe if probing of devices will happen during suspend or
* hibernation and system behavior will be unpredictable in this case.
* So, let's prohibit device's probing here and defer their probes
* instead. The normal behavior will be restored in dpm_complete().
*/

Because the device probe is deferred, the qcom_mhi_qrtr_probe() is not
called and thus MHI channels are not prepared:

So what this means that QRTR is not delivering messages and the QMI connection
is not working between ath11k and the firmware, resulting a failure in firmware
initialization.

To fix this add new function mhi_power_down_keep_dev() which doesn't destroy
the devices for channels during power down. This way we avoid probe defer issue
and finally can get ath11k hibernation working with the following patches.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30

Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com>
---
drivers/bus/mhi/host/internal.h | 4 +++-
drivers/bus/mhi/host/pm.c | 42 ++++++++++++++++++++++++++++-----
include/linux/mhi.h | 18 +++++++++++++-
3 files changed, 56 insertions(+), 8 deletions(-)

diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
index 5fe49311b8eb..aaad40a07f69 100644
--- a/drivers/bus/mhi/host/internal.h
+++ b/drivers/bus/mhi/host/internal.h
@@ -80,6 +80,7 @@ enum dev_st_transition {
DEV_ST_TRANSITION_FP,
DEV_ST_TRANSITION_SYS_ERR,
DEV_ST_TRANSITION_DISABLE,
+ DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE,
DEV_ST_TRANSITION_MAX,
};

@@ -90,7 +91,8 @@ enum dev_st_transition {
dev_st_trans(MISSION_MODE, "MISSION MODE") \
dev_st_trans(FP, "FLASH PROGRAMMER") \
dev_st_trans(SYS_ERR, "SYS ERROR") \
- dev_st_trans_end(DISABLE, "DISABLE")
+ dev_st_trans(DISABLE, "DISABLE") \
+ dev_st_trans_end(DISABLE_DESTROY_DEVICE, "DISABLE (DESTROY DEVICE)")

extern const char * const dev_state_tran_str[DEV_ST_TRANSITION_MAX];
#define TO_DEV_STATE_TRANS_STR(state) (((state) >= DEV_ST_TRANSITION_MAX) ? \
diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
index 8b40d3f01acc..11c0e751f223 100644
--- a/drivers/bus/mhi/host/pm.c
+++ b/drivers/bus/mhi/host/pm.c
@@ -468,7 +468,8 @@ static int mhi_pm_mission_mode_transition(struct mhi_controller *mhi_cntrl)
}

/* Handle shutdown transitions */
-static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
+static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
+ bool destroy_device)
{
enum mhi_pm_state cur_state;
struct mhi_event *mhi_event;
@@ -530,8 +531,16 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
dev_dbg(dev, "Waiting for all pending threads to complete\n");
wake_up_all(&mhi_cntrl->state_event);

- dev_dbg(dev, "Reset all active channels and remove MHI devices\n");
- device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_destroy_device);
+ /*
+ * Only destroy the 'struct device' for channels if indicated by the
+ * 'destroy_device' flag. Because, during system suspend or hibernation
+ * state, there is no need to destroy the 'struct device' as the endpoint
+ * device would still be physically attached to the machine.
+ */
+ if (destroy_device) {
+ dev_dbg(dev, "Reset all active channels and remove MHI devices\n");
+ device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_destroy_device);
+ }

mutex_lock(&mhi_cntrl->pm_mutex);

@@ -821,7 +830,10 @@ void mhi_pm_st_worker(struct work_struct *work)
mhi_pm_sys_error_transition(mhi_cntrl);
break;
case DEV_ST_TRANSITION_DISABLE:
- mhi_pm_disable_transition(mhi_cntrl);
+ mhi_pm_disable_transition(mhi_cntrl, false);
+ break;
+ case DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE:
+ mhi_pm_disable_transition(mhi_cntrl, true);
break;
default:
break;
@@ -1175,7 +1187,8 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
}
EXPORT_SYMBOL_GPL(mhi_async_power_up);

-void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
+static void __mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful,
+ bool destroy_device)
{
enum mhi_pm_state cur_state, transition_state;
struct device *dev = &mhi_cntrl->mhi_dev->dev;
@@ -1211,15 +1224,32 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
write_unlock_irq(&mhi_cntrl->pm_lock);
mutex_unlock(&mhi_cntrl->pm_mutex);

- mhi_queue_state_transition(mhi_cntrl, DEV_ST_TRANSITION_DISABLE);
+ if (destroy_device)
+ mhi_queue_state_transition(mhi_cntrl,
+ DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE);
+ else
+ mhi_queue_state_transition(mhi_cntrl,
+ DEV_ST_TRANSITION_DISABLE);

/* Wait for shutdown to complete */
flush_work(&mhi_cntrl->st_worker);

disable_irq(mhi_cntrl->irq[0]);
}
+
+void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
+{
+ __mhi_power_down(mhi_cntrl, graceful, true);
+}
EXPORT_SYMBOL_GPL(mhi_power_down);

+void mhi_power_down_keep_dev(struct mhi_controller *mhi_cntrl,
+ bool graceful)
+{
+ __mhi_power_down(mhi_cntrl, graceful, false);
+}
+EXPORT_SYMBOL_GPL(mhi_power_down_keep_dev);
+
int mhi_sync_power_up(struct mhi_controller *mhi_cntrl)
{
int ret = mhi_async_power_up(mhi_cntrl);
diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index 77b8c0a26674..cde01e133a1b 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -630,12 +630,28 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl);
int mhi_sync_power_up(struct mhi_controller *mhi_cntrl);

/**
- * mhi_power_down - Start MHI power down sequence
+ * mhi_power_down - Power down the MHI device and also destroy the
+ * 'struct device' for the channels associated with it.
+ * See also mhi_power_down_keep_dev() which is a variant
+ * of this API that keeps the 'struct device' for channels
+ * (useful during suspend/hibernation).
* @mhi_cntrl: MHI controller
* @graceful: Link is still accessible, so do a graceful shutdown process
*/
void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful);

+/**
+ * mhi_power_down_keep_dev - Power down the MHI device but keep the 'struct
+ * device' for the channels associated with it.
+ * This is a variant of 'mhi_power_down()' and
+ * useful in scenarios such as suspend/hibernation
+ * where destroying of the 'struct device' is not
+ * needed.
+ * @mhi_cntrl: MHI controller
+ * @graceful: Link is still accessible, so do a graceful shutdown process
+ */
+void mhi_power_down_keep_dev(struct mhi_controller *mhi_cntrl, bool graceful);
+
/**
* mhi_unprepare_after_power_down - Free any allocated memory after power down
* @mhi_cntrl: MHI controller
--
2.25.1